Fuel oil composition and composite improvement agent therefor



United States Patent 3,116,128 FUEL 0H. CQMPGSHTION AND COMPOSlTEIMFERG'VEMENT AGENT THEREFOR Elizabeth L. Fareri, Pittsburgh, and EdwardMitchell,

Valencia, Pa, assiguors to Gulf Research & Development Company,Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Dec. 28,U59, Ser. No. 862,040 11 Claims. (Cl. 44--71) This invention relates toimproving the combustion characteristics of hydrocarbon oil fuels thatnormally tend to form substantial amounts of soot and smoke duringcombustion, and to improvement agents adapted for use in such fuels.

The petroleum industry has encountered a serious problem in satisfyingthe demand for middle distillate and heavier fuel oils that can beburned in fuel burners, such as those of the atomizing type and of therotary Wall flame type, with little or no accompanying formation ofsmoke or soot. Oils that are normally burned in oil burners of the typesindicated are those of No. 2 grade or heavier, although somewhat lighteroils can be used. Although some smoke and soot formation may accompanycombustion of any hydrocarbon oil where less than optimum combustionconditions are used, the problem is serious in the case of oils havingan API gravity of less than 34, as substantial smoking and sootformation will occur during combustion of such oils even when favorablecombustion conditions are employed. The poor combustion characteristicsof such oils are considered attributable to the relatively highproportion of aromatic com ponents contained therein. Fuel oils havingan API gravity of less than 34 will normally contain in excess of about20 percent aromatics, for example, 25, 40, or even 60 percent or more ofaromatic components, whereas lighter fuel oils will normally contain asubstantially lower proportion of aromatics, for example, 15 percent orless. In the case of distillate oils, a high aromatics content usuallysignifies a large proportion of cracked distillates, as the latter arerelatively rich in aromatics. The proportion of catalytically crackeddistillate fuel oils in commercially marketed fuel oils has increased inrecent years notwithstanding the relatively inferior burning qualitiesof such oils, because the demand for fuel oils of comparable boilingrange has exceeded the available supply of straight-run oils.

Not only do low API gravity distillate oils containing large proportionsof cracked distillate, that is, oils rich in aromatics, form greaterquantities of soot during combustion than straight-run, high API gravitydistillate oils, or similar oils low in aromatics, but also such oilsform soot of different quality. Soot formed from the latter oils is aloosely deposited, low-density material having a low coefiicient of heattransfer, whereas soot from the former oils is resinous, much denser andhas a higher coefficient of heat transfer.

While the problem of obtaining clean combustion is especially serious inthe case of distillate fuels, where fuel quality is of major importance,a combustion problem also exists in the case of residual fuel oils.Residual fuels, similarly as middle distillate fuel oils, have an APIgravity less than 34 (API gravity for typical No. 6 fuel oils varies inthe range of about to and they also frequently contain exceptionallylarge proportions, for example 60 percent or more, of aromaticcomponents. Residual fuels can contain relatively low-boiling aromaticcomponents as well as higher boiling materials, as they are frequentlydiluted or cut back with lower boiling cracked distillate oils in orderto reduce the viscosity of the heavier oils.

Although the combustion of fuel oils having an API gravity of less than34, and consequently a relatively large proportion of aromatics, willtend to produce soot and smoke in atomizing-type burners, that is,burners in which the fuel oil is burned in the form of a spray of liquiddroplets after mixture with air, combustion of such oils in rotarywall-flame type burners constitutes an especially severe problem. In thelatter instance the fuel oil is burned in vapor form after vaporizationof the fuel by impingement thereof on a hot metal surface.

Excessive smoking and soot formation during combustion of fuel oils isobjectionable not only from the standpoint of cleanliness and airpollution, but also in that smoke and soot lead to stack deposits whichmay reduce burner draft and/ or cause the stack temperature to rise to adangerous point.

The present invention relates to improvement of hydrocarbon fuel oilsthat normally exhibit smoke and sootforming tendencies duringcombustion, whereby such oils are rendered more suitable for use asfuels in domestic oil burners of various types such as heating furnacesof the atomizing or rotary wall-flame type, combustion gas turbineengines, diesel engines, and the like. We have found that such improvedfuel compositions can be obtained by incorporating in a fuel oil thatnormally tends to form substantial smoke and soot during combustionabout 0.005 to about 2 percent, preferably about 0.02 to 0.05 percent byweight of a combination of (a) a preferentially oil-soluble secondary ortertiary amine at least one of whose N-substituents is an open-chain orcyclic, saturated or unsaturated aliphatic hydrocarbon substituent or anaromatic hydrocarbon substituent, including alkaryl and aralkyl,containing 6 to 22 carbon atoms, preferably 8 to 18 carbon atoms,another of whose N- substituents is an aliphatic hydrocarbon radicalthat contains 1 to 22 carbon atoms and that is either saturated orunsaturated and either unsubstituted or substituted with nonhydrocarbonsubstituents such as hydroxyl, amino, or halogen, or the like, and whoseremaining N-substituent is either hydrogen or a substituent of the sameclass as either of the previously described N-substituents, and (b) analkali metal, alkaline earth metal, ammonium or ethylolammoniumdialkylsulfosuccinate whose alkyl groups each contain 7 to 9 carbonatoms, at least 6 of which are in a straight chain, but there being nogroup containing more than 7 carbon atoms attached to the alpha-carbonatom of said alkyl groups. Insofar as the amine component is concerned,amines containing secondary amino groups are considered especiallyeffective, a preferred example being 3-dodecylaminopropylamine. Anexample of a preferred tertiary amine is N,N-di-npropylaniline. However,other secondary and tertiary amines of the class indicated can be used.The dioctylsulfosuccinates are especially valuabledialkylsulfosuccinates for the purposes of this invention, sodium di(2-ethylhexyl)sulfosuccinate being an example of a preferred salt. However,the use of other dialkylsulfosuccinates within the class disclosed isincluded by the present invention. The amines and thedialkylsulfosuccinates can be employed in fueloils in varyingproportions with respect to each other provided that each is present inan amount of at least 0.0025 percent and preferably 0.005 to 0.05percent by weight of the oil, but larger amounts of each can be used.The present invention includes not only the compounded fuel oilscontaining the above-indicated combination of improvement agents, butalso the combination of improvement agents, as such. In such form wenormally prefer to employ the respective components of the combinationin a weight ratio of about 1:20 to 20:1, and more preferably about 1:5to 5:1. However, other proportions can be used.

The exact mechanism by which the combination of improvement agents ofthe above-indicated classes functions to reduce smokeand soot-formingtendencies of fuel oils has not been definitely determined, andaccordingly, We do not intend the present invention to be limited to anyparticular theory of operation. It may be that the combination ofimprovement agents disclosed herein reduce smoke and soot formation atleast in part by reducing the ignition temperature of the oil, wherebymore complete combustion of the oil may be obtained, and whereby at thesame time the possibility of thermal cracking of the fuel oil prior tocombustion is reduced. The above-indicated mechanism is more or lesssuggested by the fact that the herein disclosed combinations ofimprovement agents have been found to improve the ignitioncharacteristics of fuel oils. However, it may be that the combinationsof improvement agents disclosed herein function at least in part byreducing the particle size of the fuel droplets in the combustion zoneand by improving the fuel spray pattern in the combustion zone. In anyevent, regardless of the mechanism by which the combinations ofimprovement agents disclosed herein may function, aavilable experimentalevidence demonstrates that the mixtures of amines anddialkylsulfosuccinates disclosed herein act in combination to produce amarked reduction in smokeand soot-forming tendencies that is greaterthan might be expected from the effect of the individual materialsthemselves.

As indicated above the preferred dialkylsulfosuccinate for the purposesof this invention is sodium di(2-ethylhexyl)sulfosuccinate. However, theinvention is not limited to the use of this material and otherequivalent dialkylsulfosuccinates can be used. Thedialkylsulfosuccinates that are useful for the purposes of thisinvention are those having a Draves Wetting power value of about 0.15 to0.5, and preferably 0.15 to 0.25. This class of salts can be representedby the following formula:

(IJOOR 000R where C, H, O and S are, respectively, carbon, hydrogen,oxygen and sulfur; where R is an alkyl group containing 7 to 9 carbonatoms, at least 6 of which are in a straight chain, there being no groupattached to the alpha carbon atom of said alkyl groups containing morethan 7 carbon atoms; Where Z is a salt-forming group selected from theclass consisting of alkali metal, alkaline earth metal, ammonium andethylolammonium, and Where n is an integer equal to the valence of Z. Inthe foregoing general formula, R can represent identical or differentalkyl groups of the type specified above.

Especially effective results are obtained by the use of alkali metaldialkylsulfosuccinates wherein the alkyl groups are branched and contain8 carbon atoms. An example of a dialkylsulfosuccinate with whichexcellent results have been obtained is the sodium salt ofdi(2-ethylexyl)sulfosuccinate, the formula of which is;

H Cir-I II- 3oooCHZc' (oHt)3oH l 1'1 I t H-oo0ooH2C(CHn oH3 SO Na 02115where Na is sodium and C, H, O, and S are as indicated above.

Examples of other dialkylsulfosuccinates, the use of which is includedby this invention, are the sodium, potassium, calcium, barium, ammonium,and triethylolammonium salts of di(n-heptyl), di(n-octyl),di(1-methylhexyl) di l-butylamyl) -di( 1-isobuty1-3-methylbutyl)di(2-ethylhexyl), di(l-methylheptyl), and di(1-rnethyl-4- ethylhexyl)sulfosuccinates. Examples of salts of mixed esters that are suitable forthe purposes of this invention are the sodium, potassium, calcium,barium, ammonium and triethylolammonium salts ofmono-2-ethylhexylmono-l-methyl-4-ethylhexylsulfosuceinate, and mono-2-ethylhexyl-mono-1-methylheptylsulfosuccinate.

"In general, any preferentially oil-soluble secondary or tertiary amineof the class indicated above can be used for the purposes of thisinvention. The amine employed should be preferentially oil-soluble toavoid excessive leaching of the amine from the oil by Water with whichthe oil is contacted during shipment and storage. In general, the classof amines whose use is included by this invention can be represented bythe general formula:

a where R is an open-chain or cyclic, saturated or unsaturated aliphatichydrocarbon radical or an aromatic hydrocarbon radical, including bothalkaryl and aralkyl groups, containing 6 to 22 carbon atoms, andpreferably 8 to 18 carbon atoms, examples of which are n-hexyl,Z-ethylhexyl, Oxo-octyl, n-dodecyl, n-octadecenyl, n-oct-adecadienyl,phenyl, tolyl, benzyl, and naphthyl, where R is an aliphatic hydrocarbonradical containing 1 to 22 carbon atoms that is either unsubstituted orsubstituted with nonhydrocarbon substituents such as amino, hydroxyl,\or halogen, examples of such groups being methyl, ethyl, isopropyl,hydroxyethyl, aminoethyl, aminoprop-yl, and chlorobutyl, and radicals ofthe same kind as R and where R is hydrogen or a radical of the sameclass as R or R As will be apparent, the nature of the R and RN-substituents is less critical than that of the R N- substituent. Theimportant consideration insofar as the R and R substituents areconcerned is that one or both must be a group other than hydrogen so asto create the necessary secondary or tertiary amino functional groupwhose presence is essential for the purposes of this invention.

The amines and dialkylsulfosuccinates disclosed herein can be employedin fuel oils in any proportion that will reduce the smoke andsoot-forming tendencies of the oils. Naturally, the individual aminesand dialkylsulfosuccinates of the classes disclosed herein are not exactequivalents, nor are all the individual fuel oils disclosed hereinequally responsive to the addition agents disclosed herein. Accordingly,the optimum amounts of each components of the mixed addition agentsdisclosed herein may vary according to the nature of the amine, thedialkylsulfosuccinate and the fuel oil. Normally, some improvement inthe combustion characteristics of a fuel oil of the kind disclosedherein will be obtained by the use of as little as 0.0025 percent of thedialkylsulfosuccinate, and the improvement thus obtained can be promutedby the concurrent use of as little as 0.0025 percent by Weight of amine.Best results from the standpoint of combustion improvement are usuallyobtained with proportions of about 0.005 to about 0.05 percent each ofthe amine and the dialkylsulfosuccinate. Up to 2 percent of thecombination of amine and dialkylsulfosucoinate can be used if desired,provided that each component is present in the proportion of at least0.0025 percent by Weight of the oil. Even greater amounts can be used,but no additional advantages are obtained from the standpoint ofcombustion improvement by such use.

The amines. and dialkylsulfosuccinates disclosed herein can be added tothe fuel oils whose combustion characteristics are to be improved eithersingly or in combination, and either as such, or in the form ofconcentrated solutions in solvents such as kerosene, toluene, or butylalcohol. 'If desired, the combination of improvement agents may alsohave included therewith other addition agents designed to improve one ormore properties of the fuel oil. Some stirring is desirable when mixingthe amine and dialkylsulfosuccinate with the oil to facilitate rapidformation of a homogeneous mixture. However, stirring is not essential.

As indicated the amine-dialkylsulfosuccinate mixtures disclosed hereinare useful in conjunction with any fuel oil that normally tends to formsubstantial amounts of smoke and soot during combustion. Such oils arenormally of the middle distillate or heavier fuel oil grades such as theso-called No. 2, No. 4, No. 5, and No. 6 fuel oils and the use of suchoils is included by the present invention. Fuel oils of these grades aredefined in the ASTM Standards on Petroleum Products and Lubricants underthe ASTM specification D396. The invention is especially important inconnection with fuel oils having an API gravity of less than 34",particularly when these oils contain an excess of about 20 percentaromatic'hydrocarbons, as such oils involve serious smoke andsootforming problems.

In order to demonstrate the effectiveness of the combustion improvingmixtures disclosed herein, representative aminedialkylsulfosuccinatemixtures were incorporated in separate samples of a No. 2 fuel oil inproportions of 0.03 percent by weight. Each of these fuel samples and asample of uninhibited fuel oil were then subjected to a one-day smoketest. In order to demonstrate the combined eifect of the amines anddialkylsulfosuccinates disclosed herein, tests were also carried out onsamples of the fuel oil that contain only the amines and only thedialkylsulfosuccinate alone.

The one-day smoke test was carried out in a domestic oil burner (TimkenModel 0BC110). Conventional burner controls were associated with thetest apparatus in conjunction with electrical timer relays to provide a20-minute on, -minute off cycle of burner operation. After permitting awarm-up of at least one minute on cycle of burner operation with maximumcombustion air, smoke spot and CO readings were taken Viscosity, SUV,See, at 100 F 34.1 Flash, P-M, F 180 Pour point, F -10 Color, ASTM union2 Sulfur, L., percent 0.54 Carbon residue, Conradson, percent on 10%bottoms 0.32 Distillation, gas oil ASTM D 158-54:

Over point, F 382 End point, "F 10% distilled at, F distilled at, F 90%distilled at, F

5 62 Recovery, percent 99.0

The results of the foregoing tests are presented in the following table,wherein in Examples I and II, the aminedialkylsulfosuccinate mixturesemployed are specific embodiments of the mixed addition agents, apartfrom the compounded fuel oil, that are useful for the purposes of thepresent invention.

Residue, percent Table A Blank Sodium Blank Blank Di(2- N ,N-Di-n-3-Dode- Example Exa ple Test Fuel Blank Ethyl- Propylcyl-Amino I I1I-IexyD- Aniline Propyl- Sullo-Sucamin cinate Sample Make-Up:

Hydrogenated WISR N0. 2 Fuel Oil Distillate, percent Vol 17. 5 17. 5 17.5 17. 5 17. 5 l7. 5 FCC Light Catalytic Gas Oil, percent vol 82. 5 82. 582. 5 82. 5 82. 5 82. 5 Improvement Agon t, percent wt.

added, 50% Solution of Sodium DiQ-EthylhexyDSulfosuccinate in n-ButylAlcohoL. 0.02 0. 02 0.02 N,N-Di-n-Propylaniline 1 0.02 0. O2S-Dodecylaminopropylanliue 0. 02 0. 02 Inspection:

Smoke v. CO2 Performance Test, Timken Model 0130-110, Oilboiler II,Average Rate of Oil Flow 6.84 lb.lhr.

Avg. Smoke Spot No. in the 10 13% CO1 Burning Range 2. 76 2.15 3.10 2.65 1.86 1.75 Avg. Reduction in Smoke Spot No. in the 10-13% 002 BurningRange 22. 1 *+12. 3 4.0 32. 5 36.6

*Incrcase in Smoke Spot Number.

at the middle of each on cycle for several cycles using different airgate settings to regulate the quantity of com bustion air. Changes ofgate setting were made during burner off phases of the cycle. Smoke spotreadings were obtained by withdrawing flue gas from a sampling probeinstalled in the chimney pipe through a disc of No. 4 Whatman filterpaper one inch in diameter for two minutes. A vacuum pump was used tomaintain a pressure differential of 2 /4 inches Hg across the disc. Thesmoke spot reading was determined by means of a photo cell meter whichhad been calibrated by using a Bacharach-Shell smoke spot chartgraduated in increasing shades of black ranging from 0 (clean disc) to 9(black disc) as the standard. CO readings were obtained by withdrawingflue gas through a sampling probe installed in a chimney pipe (inaccordance with US. Department of Commerce Bulletin CA104-46) and byanalyzing the Comparison of the results obtained in connection with theExample I and Example II test fuel compositions, which containedamine-dialkylsulfosuccinate mixtures of the class disclosed herein, withthe results obtained for the uninhibited fuel test sample and for thefuel test samples containing only amine or only dialkylsulfosuccinateclearly shows that the additive mixtures of the class disclosed hereinproduce much better results than might be expected from the resultsobtained with each improvement agent individually.

In order further to demonstrate the improvement in combustioncharacteristics obtainable by the addition agent mixtures disclosedherein, another sample: of a No. 2 fuel oil that normally tended to formsubstantial amounts of smoke and soot during combustion and containingstill another amine-dialkylsulfosuccinate mixture was subjected to a10-day deposits combustion test. In accordance with this test procedurethe same furnace described in the preceding test was operated similarlyas described except that the test was run for seven hours of cyclicoperation each day for days. Upon completion of the test, the sootdeposits were collected from the heating surfaces of the furnace andweighed. In order to form a basis for comparison a test was also run ona sample of the oil containing only the amine.

The base fuel employed in the 10-day deposits test was a commercial-typeNo. 2 fuel oil having an API gravity of 295 and consisting of 35 percentby volume West Texas straight-run No. 2 fuel oil distillate and 65percent by volume fiuid catalytically cracked No. 2 fuel oil distillateshaving an aromatics content of 44.1 weight percent (calculated), andhaving a distillation range of about 354 to 621 F. and a 90 percent ASTMdistillation point of 572 F., and having a carbon residue on 1-0 percentbottoms of 0.50 percent. The base fuel also contained 0.003 percent byweight of a commercial alkylamine phosphate corrosion inhibitor, whichhad no significant effect on the combustion characteristics of the oils.

The amine employed in the 10-day deposits test was a commercial mixtureof secondary and tertiary amines marketed under the name Santolene l. Asample of the amine mixture employed in the test was fractionallydistilled to form a fraction having a boiling range of 221 to 225 C. andan average nitrogen content of 7.15 weight percent, a fraction having aboiling range of 230 to 232 C. and an average nitrogen content of 7.09weight percent, a fraction having a boiling range of 241 to 248 C. andan average nitrogen content of 6.0 weight percent, and a From theforegoing resuits it will be seen that the amine-dialkylsulfosuccinatemixtures of the kind disclosed herein are capable of effecting asubstantial reduction in combustion deposits within the burner and thatthey are also capable of effecting an improvement in the ignitioncharacteristics of the oil.

It will be understood that the specific embodiments set forthhereinabove are illustrative only and that the invention is not limitedto the use of such specific combinations and that other amines anddialkylsulfosuccinates disclosed herein can be employed. For example,good results are obtainabie by the substitution in the foregoingcompounded fuel compositions in the same or equivalent amounts of thesodium, potassium, calcium, barium, ammonium, and triethylolammoniumsalts of di(n-heptyl), di(n-octyl), di(1-methylhexyl), di(1-butylamyl),di(1 isobutyl-3-methylbutyl), di(2 ethylhexyl), di(l met-hylheptyi), anddi(l-methyl-4-ethylhexyl) esters of sulfosuccinic acid and by thesubstitution of the same or equivalent amounts of di-n-hexylamine,di-2-ethylhexylamine, di(Oxo-octyl)amine, dicocoamine (Armeen 2C),dicyclohexylamine, N-methyl-aniline, tri(Oxo-octyl)- amine,N,N-diisopropylbenzylamine, diphenylamine, N-isopropyl-p-rnethylaniline, N,N-dimethyl-p-methylaniline,N-propylaniline, N,N-diethyl-m-toluidine, N,N-dibutylbenzylamine,N-propyl-o-methylaniline, N-isobutylaniline, and N,N-diisobutylaniline.

Specific examples of other amine-dialkylsulfosuccinate mixtures that areuseful for the purposes of this invention and exampies of othercompounded fuel oils containing the same are indicated in the followingtable:

Table C Combination Improvement Agent, Solution of 1:1 Wt. Ratio Mixturein Wt.

n-Butyl Alcohol Percent Fimmnlp Improvc- Base Fuel ment AmineDialkylsuliosuccinate Agent 3-Oleylaminopropylamine- CalciumDioctylsullosuccinate 0. 04 Exulnple I Fuel 1 3-0lcylaminopropylaminaSodium Dioctylsulfosuccinate 0. 04 Do. N-Isopropyl-p-Methylani-Triethylolammonium Dioctylsulfosuccinate. 0. 04 D0.

line. N-Propylaniline Potassium Diheptylsulfosuccinate 0. 04 Do.N-Butylbenzylamine Ammonium Di(1-l lcthylhexyl)-sulfosuccinate... 0. 04D0. N,N-Diisobutylaniline Barium Ditl-Butylamyl)-sullosuccinate 0. 04D0. Di-Oxo-Octylamine Sodium Di(l-Isobutyl-3-Methylbutyl)sulfosuc- 0.08102 API Gravity,

einatc. N o. 6 Fuel Oil.

fraction having a boiling range of 274 to 276 C. and an average nitrogencontent of 4.20 weight percent. Each fraction gave positive tests forsecondary and tertiary amines. Each of the above fractions wasidentified as a mixture of amines, as no solid derivatives wereobtainable. On the basis of boiling points, the amine mixture appears tocomprise mainly secondary and tertiary aromatic amines. The residue fromthe distillation contained surf ur and nitrogen. An original sample ofthe mixed amines was found to contain 6.01 percent by weight nitrogenand 0.29 percent by Weight sulfur.

The results of the 10-day deposits test were as follows:

If desired the fuel oil compositions of this invention may contain inaddition to the compounds previously discussed oxidation inhibitors,corrosion inhibitors, antifoam agents, other ignition qualityimprovement agents, sludge inhibitors, color stabilizers, and/or otheraddition agents adapted to improve the oils in one or more respects.

Obviously, other modifications and variations of the invention as hereindescribed may be resorted to Without departing from the spirit or scopethereof. Therefore, only such limitations will be imposed as areindicated in the appended claims.

We claim:

1. A fuel oil composition comprising a major amount of a hydrocarbonfuel oil that normally tends to form smoke and soot during combustion,and containing an amount sufiicient to reduce the smoke and soot-formingtendencies of the oil in the range of about 0.005 to about 2.0 percentby weight of a combination of (a) a preferentially oil-soluble member ofthe group consisting of secondary and tertiary amines at least one ofwhose N- substituents is selected from the group consisting ofhydrocarbon radicals containing 6 to 22 carbon atoms, another of whoseN-substituents is an aliphatic hydrocarbon radical containing 1 to 22carbon atoms and whose remaining N-substituent is selected from thegroup consisting of hydrogen and a radical of the same class as the twopreviously described N-suostituents, and (b) a member selected from thegroup consisting of alkali metal, alkaline earth metal, ammonium, andethylolammonium salts of a dialkyl-sulfosuccinate whose alkyl groupseach contain 7 to 9 carbon atoms, at least six of which are in astraight chain, but there being no group containing more than 7 carbonatoms attached to the alpha-carbon atom of said alkyl groups, each ofsaid amine and said salt of said dialkylsulfosuccinate being present inan amount of at least 0.0025 percent by weight of the oil.

2. The composition of claim 1 where said fuel oil is a distillate fueloil.

3. The fuel oil composition of claim 1 where said hydrocarbon fuel oilhas an API gravity less than about 34.

4. The composition of claim 1 where the amount of said combination isabout 0.01 to 0.1 percent by weight and each of said amine and said saltof said dialkylsulfosuccinate is present in an amount of at least about0.005 percent by weight of the oil.

5. The fuel oil composition of claim 1 where said amine is a secondaryamine, one of whose N-substituents is an aliphatic hydrocarbon radical,another of whose N-substituents is an amino-substituted aliphatichydrocarbon radical, and Whose remaining N-substituent is hydrogen.

6. A fuel oil composition comprising a major amount of a hydrocarbonfuel oil that normally tends to form smoke and soot during combustionand containing an amount suiiicient to reduce the smoke and soot-formingtendencies of the oil in the range of about 0.005 to 2.0 percent byweight of the oil of a combination of N,N-din-propylaniline and sodiumdioctylsulfosuccinate, each of said N,l I-di-n-propylaniline and saiddioctylsulfosuccinate being present in the oil in an amount of at leastabout 0.0025 percent by weight of the oil.

7. A fuel oil composition comprising a major amount of a hydrocarbonfuel oil that normally tends to form smoke and soot during combustion,and containing an amount sufiicient to reduce the smoke and soot-formingtendencies of the oil in the range of about 0.005 to 2.0 percent byWeight of the oil of S-dodecyl-aminopropylamine, and sodiumdioctylsulfosuccinate, each of said 3- dodecylaminopropylamine and saiddioctylsulfosuccinate being present in an amount of at least about0.0025 percent by weight of the oil.

8. A composition adapted to improve the combustion characteristics ofhydrocarbon fuel oils that normally tend to form smoke and soot duringcombustion, consisting essentially of a combination of (a) apreferentially oilsoluble member of the group consisting of secondaryand tertiary amines at least one of whose N-substituents is selectedfrom the group consisting of hydrocarbon radicals containing 6 to 22carbon atoms, another of Whose N- substituents is an aliphatichydrocarbon radical containing 1 to 22 carbon atoms and whose remainingN-substituent is selected from the group consisting of hydrogen and aradical of the same class as the two previously describedN-substituents, and (b) a member selected from the group consisting ofalkali metal, alkaline earth metal, ammonium, and ethylolammonium saltsof a dialkyl-sulfosuccinate whose alkyl groups each contain 7 to 9carbon atoms, at least six of which are in a straight chain, but therebeing no group containing more than 7 carbon atoms attached to thealpha-carbon atom of said alkyl groups, each of said amine and said saltof said dialkylsulfosuccinate being present in the Weight ratio of about1:20 to 20:1.

9. The composition of claim 8 where said amine is a secondary amine, oneof whose N-substituents is an aliphatic hydrocarbon radical, another ofWhose N-substit uents is an amino-substituted aliphatic hydrocarbonradical, and whose remaining N-substituent is hydrogen.

10. A composition adapted to improve the combustion characteristics ofhydrocarbon fuel oils that normally tend to form smoke and soot duringcombustion, comprising a combination of N,N-di-n-propylaniline andsodium dioctylsulfosuccinate, each of said N,N-di-n'propylaniline andsaid dioctylsulfosuccinate being present in the combination in a weightratio of about 1:5 to 5:1.

11. A composition adapted to improve the combustion characteristics ofhydrocarbon fuel oils that normally tend to form smoke and soot duringcombustion, comprising a combination of 3-dodecylaminopropylamine andsodium dioctylsulfosuccinate, each of said 3-dodecylaminopropylamine andsaid dioctylsulfosuccinate being present in the combination in a Weightratio of about 1:5 to 5:1.

References Cited in the file of this patent UNTTED STATES PATENTS Wieset al Dec. 25, 1951 Caron et a1. July 20, 1954 OTHER REFERENCES

1. A FUEL OIL COMPOSITION COMPRISING A MAJOR AMOUNT OF A HYDROCARBONFUEL OIL THAT NORMALLY TENDS TO FORM SMOKE AND SOOT DURING COMBUSTION,AND CONTAINING AN AMOUNT SUFFICIENT TO REDUCE THE SMOKE AND SOOT-FORMINGTENDENCIES OF THE OIL IN THE RANGE OF ABOUT 0.005 TO ABOUT 2.0 PERCENTBY WEIGHT OF A COMBINATION OF (A) A PREFERENTIALLY OIL-SOLUBLE MEMBER OFTHE GROUP CONSISTING OF SECONDARY AND TERTIARY AMINES AT LEAST ONE OFWHOSE NSUBSTITUENTS IS SELECTED FROM THE GROUP CONSISTING OF HYDROCARBONRADICALS CONTAINING 6 TO 22 CARBON ATOMS, ANOTHER OF WHOSEN-SUBSTITUENTS IS AN ALIPHATIC HYDROCARBON RADICAL CONTAINING 1 TO 22CARBON ATOMS AND WHOSE REMAINING N-SUBSTITUENT IS SELECTED FROM THEGROUP CONSISTING OF HYDROGEN AND A RADICAL OF THE SAME CLASS AS THE TWOPREVIOUSLY DESCRIBED N-SUBSTITUENTS, AND (B) A MEMBER SELECTED FROM THEGROUP CONSISTING OF ALKALI METAL, ALKALINE EARTH METAL, AMMONIUM, ANDETHYLOLAMMONIUM SALTS OF A DIALKYL-SULFOSUCCINATE WHOSE ALKYL GROUPSEACH CONTAIN 7 TO 9 CARBON ATOMS, AT LEAST SIX OF WHICH ARE IN ASTRAIGHT CHAIN, BUT THERE BEING NO GROUP CONTAINING MORE THAN 7 CARBONATOMS ATTACHED TO THE ALPHA-CARBON ATOM OF SAID ALKYL GROUPS, EACH OFSAID AMINE AND SAID SALT OF SAID DIALKYLSULFOSUCCINATE BEING PRESENT INAN AMOUNT OF AT LEAST 0.0025 PERCENT BY WEIGHT OF THE OIL.